Exposure to particulate matter mass and species during pregnancy and risk of birth at preterm gestational ages

Rappazzo, Kristen

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March 19, 2019

Creator

Rappazzo, Kristen
- Affiliation: Gillings School of Global Public Health, Department of Epidemiology

Abstract

Particulate matter <2.5 micrometers in aerodynamic diameter (PM2.5) has been variably associated with preterm birth (PTB), but the roles of PM2.5 species have been less studied. In this work we examine associations between PM2.5 mass and four PM2.5 species and PTB. We estimated risk of birth in 4 preterm categories (risks reported as PTBs per 106 pregnancies) associated with change in ambient concentrations of PM2.5 mass, elemental carbon (EC), organic carbons (OC), nitrates (NO3), and sulfates (SO4). From live birth certificates, we constructed a cohort of singleton pregnancies reaching 20 weeks of gestation between 2000-2005 (n=1,940,213; 8% PTB). We estimated mean exposures for each week of gestation from monitor-corrected Community Multi-Scale Air Quality modeling data. Risk differences (RD (95% confidence intervals)) for PTB categories (defined by gestational ages 20-27, 28-31, 32-34, and 35-36) were estimated for each exposure using modified Poisson linear regression, adjusted for maternal race, marital status, education, age, and ozone. RD estimates varied by exposure window, outcome period, and pollutant. Exposure to PM2.5 at week four of gestation resulted in generally elevated risks, though magnitude varied by PTB category (e.g., for a 1μg/m3 increase RD=11.8 (-6, 29.2); RD=46 (23.2, 68.9); RD=61.1 (22.6, 99.7); and RD=28.5 (- 39, 95.7) for birth at weeks 20-27, 28-31, 32-34, and 35-36 respectively). Exposures anchored at time of birth were associated with positive RDs for lags of 0-2 weeks across PTB categories. EC was associated with increased risks for births between 28-34 weeks (e.g., for a 0.25μg/m3 increase in EC at gestational week 5, RD=84 (-5, 172) and RD=97 (-50, 243) for birth at weeks 28-31 and 32-34, respectively). Associations with OCs were generally null or negative. RDs for NO3 were elevated in the early weeks of gestation and null in later weeks. RDs for SO4 exposure were generally positively associated with PTB. EC and SO4 appear to be influential contributors to PM2.5’s role in PTB. Risk of PTB has diverse windows of vulnerability for exposure to species of PM2.5. Because particulate matter exposure is ubiquitous, observation indicating harm is important for influencing regulatory standards.

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